1. Field of the Invention
The present invention relates generally to a lighting apparatus using white-light Light-Emitting Diodes (LEDs), and, more particularly, to a lighting apparatus that is capable of additionally outputting light of wavelengths which is not output by a lighting apparatus using white-light LEDs and which is used to enable the human optic nerves to perform their optic functionality under natural light conditions, thereby improving both color rendering and sharpness.
2. Description of the Related Art
Fluorescent lamp lighting apparatuses are being widely used as the main lighting apparatuses of public facilities or homes. Recently, various types of lighting apparatuses using LEDs, which have half the power consumption of the fluorescent lamp lighting apparatuses, have been developed and widely used.
Meanwhile, since natural light (solar light) has a wide wavelength distribution of 380 to 780 nm and human eyesight is adapted to natural light, humans feel comfortable and, also, human eyesight can be protected when humans view objects that are illuminated with natural light.
Furthermore, it is important to make the color of the light of a lighting apparatus approximate the light color under natural light conditions by improving color rendering representative of the extent of approximating color under natural light conditions.
Therefore, conventional lighting apparatuses using LEDs have attempted to improve color rendering by combining other LEDs having various wavelengths so that the light emitted by the total LEDs can approximate natural light. However, since it is difficult to manufacture LEDs having various wavelengths due to their cost and the yields of manufacturing processes, it is common to construct lighting apparatuses using a plurality of white-light LEDs which are advantageous in terms of both manufacturing cost and yield. Such white-light LEDs are manufactured chiefly by combining blue LEDs with yellow phosphor.
Here, the white-light LEDs have a spectral distribution such as that shown in FIG. 1, and generally emit light having a first peak value in a wavelength range of about 440 to 460 nm and a second peak value in a wavelength range of about 520 to 600 nm.
However, such white-light LEDs have poor color rendering (at a level at which the Color Rendering Index (CRI) thereof is 65-75) and low sharpness because there are many wavelengths which exist in natural light but are not emitted by the white-light LEDs.